The present invention relates to a gas turbine engine, the turbine system of which is provided with a flow of cooling air over the static (non rotating) structure surrounding a stage of turbine blades, when they rotate during operation of the gas turbine engine.
It is known to form that part of the gas annulus which surrounds a stage of turbine blades from a plurality of arcuate segments. It is further known during operation of the associated engine, to direct a flow of cooling air bled from a compressor of the engine, over both inner and outer surfaces of the segments. The known art provides a single cooling air flow which is not divided so as to flow over the segments inner and outer surfaces, until it reaches some part thereof. A consequence arising from the arrangement is that insufficient cooling air flow control is available to enable direction of appropriate quantities of air to the respective surfaces. Additionally the quantities differ, one surface to the other, so that overall there is inefficient cooling.
The present invention seeks to provide a gas turbine engine including improved cooling air flow distribution.
According to the present invention, a gas turbine engine includes a stage of turbine blades surrounded by a plurality of arcuate segments, the inner surfaces of which define a part of the turbine gas annulus, each said segment including a plenum chamber at its upstream end connected in cooling air flow series with a cooling air supply via a cooling air distributing member, which member has cooling air inlets from said supply, and cooling air outlets, each cooing air inlet being in flow series with a respective pair of cooling air outlets, and wherein during operation of the associated engine, one outlet of each pair of outlets passes cooling air flow to a respective plenum chamber, and the other outlet of each said pair of outlets passes cooling air flow to the radially outer surface thereof.